Headset-hardhat adapter



FIG. 1 is a front view of a headset-hardhat adapter, showing my new design;

FIG. 2 is a perspective view thereof;

FIG. 3 is a side view thereof;

FIG. 4 is an end view thereof; and

FIG. 5 is a rear view. 

The ornamental design for a headset-hardhat adapter, substantially as shown. 